from the german word "blitzkrieg", meaning lightning (a very offensive-minded war strategy developed by the germans in WW2 that advocated quick control of your enemy's territory through fast and violent military bombardment; usually combining land and air attacks).

Used in football terminology to denoted a defensive play in which many defensive players are used to try and break through the offensive line (the line protecting the quarterbacks and running backs). A Blitz usually leaves the defence vulnerable to passing plays, but it also cuts down on the time the quarterback has to throw the ball (it's main purpose is to put pressure on the quarterback or sack the quarterback).

The Blitz referes to the Season 5 episode (aired on Monday Nov 22) of How I Met Your Mother, when one person leaves the group for any period of time and something amazing happens. You can pass on the Blitz from being part of the group when somthing amazing does happen, but another person from the group had to leave between 2-30 minutes prior to that amazing thing happening.

Robin: Barney! where did you go you missed it!
Barney: Missed what?!
Robin: We were in the thanksgiving parade!
(Prior Blitz): yea and i was there!
Barney: Awwww man!!

Also Blitz. (From BlitzMail, the trademarked name of an e-mail client developed at Dartmouth College in 1987 and still used by the students and alumni of Dartmouth, Reed College, and Washington College, as well as many residents of New Hampshire and Vermont's Upper Valley.)

the counter to the "Shotty" rule, a mad dash for the front seat of a vehicle, when two persons are in competition for the front passenger seat and the first person calls "Shotty" the second person can call "Blitz" (one may call shotty no-blitz to prevent the blitz rule from being valid)